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BACKGROUND: Obesity is a global health concern and risk factor for cardiovascular disease. The assessment of central blood pressure (cBP) has been shown to improve prediction of cardiovascular events. However, few studies have investigated the impact of obesity on cBP in adults, and invasive data on this issue are lacking. This study aimed to evaluate cBP differences between patients with and without obesity, identify cBP determinants, and evaluate the accuracy of the algorithm Antares for non-invasive cBP estimation.
METHODS: A total of 190 patients (25% female; 39% with BMI ≥30kg/m2; age: 67±12 years) undergoing elective cardiac catheterization were included. cBP was measured invasively and simultaneously estimated non-invasively using the custo screen 400 device with integrated Antares algorithm.
RESULTS: No significant cBP differences were found between obese and non-obese patients. However, females, especially those with obesity, had higher systolic cBP compared to males (P<0.05). Multiple regression analysis showed that brachial mean arterial pressure, pulse pressure, BMI, and heart rate predicted cBP significantly (adjusted R2 = 0.82, P<0.001). Estimated cBP correlated strongly with invasive cBP for systolic, mean arterial, and diastolic cBP (r = 0.74-0.93, P<0.001) and demonstrated excellent accuracy (mean difference <5 and SD <8 mmHg).
CONCLUSIONS: This study discovered no significant difference in cBP between obese and non-obese patients. However, it revealed higher cBP values in women, especially those with obesity, which requires further investigation. Additionally, the study highlights Antares\' effectiveness in non-invasively determining cBP in obese individuals. This could improve the diagnosis and treatment of hypertension in this special patient population.

Speckle contrast analysis is the basis of laser speckle imaging (LSI), a simple, inexpensive, noninvasive technique used in various fields of medicine and engineering. A common application of LSI is the measurement of tissue blood flow. Accurate measurement of speckle contrast is essential to correctly measure blood flow. Variables, such as speckle grain size and camera pixel size, affect the speckle pattern and thus the speckle contrast.
We studied the effects of spatial correlation among adjacent camera pixels on the resulting speckle contrast values.
We derived a model that accounts for the potential correlation of intensity values in the common experimental situation where the speckle grain size is larger than the camera pixel size. In vitro phantom experiments were performed to test the model.
Our spatial correlation model predicts that speckle contrast first increases, then decreases as the speckle grain size increases relative to the pixel size. This decreasing trend opposes what is observed with a standard speckle contrast model that does not consider spatial correlation. Experimental data are in good agreement with the predictions of our spatial correlation model.
We present a spatial correlation model that provides a more accurate measurement of speckle contrast, which should lead to improved accuracy in tissue blood flow measurements. The associated correlation factors only need to be calculated once, and open-source software is provided to assist with the calculation.

Upconversion broadband white light emission driven by low-power near-infrared (NIR) lasers has been reported for many materials, but the mechanisms and effects related to this phenomenon remain unclear. Herein, we investigate the origin of laser-induced continuous white light emission in synthesized nanoparticles (Gd0.89Yb0.10Er0.01)2O3 and a mechanical mixture of commercial oxides with the same composition 89% Gd2O3, 10% Yb2O3, and 1% Er2O3. We report their photophysical features with respect to sample compactness, laser irradiation (wavelength, power density, excitation cycles), pressure, temperature, and temporal dynamics. Despite the sensitizer (Yb3+) and activator (Er3+) being in different particles for the mechanical mixture, efficient discrete and continuous upconversion emissions were observed. Furthermore, the synthesized nanoparticles were developed as primary luminescent thermometers (upon excitation at NIR) in the 299-363 K range, using the Er3+ upconversion 2H11/2 → 4I15/2/4S3/2 → 4I15/2 intensity ratio. They were also operating as secondary ones in the 1949-3086 K, based on the blackbody distribution of the observed white light emission. Our findings provide important insights into the mechanisms and effects related to the transition from discrete to continuous upconversion emissions with potential applications in remote temperature sensing.

Diffuse correlation spectroscopy (DCS) is an optical technique that can be used to characterize blood flow in tissue. The measurement of cerebral hemodynamics has arisen as a promising use case for DCS, though traditional implementations of DCS exhibit suboptimal signal-to-noise ratio (SNR) and cerebral sensitivity to make robust measurements of cerebral blood flow in adults. In this work, we present long wavelength, interferometric DCS (LW-iDCS), which combines the use of a longer illumination wavelength (1064 nm), multi-speckle, and interferometric detection, to improve both cerebral sensitivity and SNR. Through direct comparison with long wavelength DCS based on superconducting nanowire single photon detectors, we demonstrate an approximate 5× improvement in SNR over a single channel of LW-DCS in the measured blood flow signals in human subjects. We show equivalence of extracted blood flow between LW-DCS and LW-iDCS, and demonstrate the feasibility of LW-iDCS measured at 100 Hz at a source-detector separation of 3.5 cm. This improvement in performance has the potential to enable robust measurement of cerebral hemodynamics and unlock novel use cases for diffuse correlation spectroscopy.

In patients on mechanical ventilation, positive end-expiratory pressure (PEEP) can decrease cardiac output through a decrease in cardiac preload and/or an increase in right ventricular afterload. Increase in central blood volume by fluid administration or passive leg raising (PLR) may reverse these phenomena through an increase in cardiac preload and/or a reopening of closed lung microvessels. We hypothesized that a transient decrease in PEEP (PEEP-test) may be used as a test to detect volume responsiveness.
Mechanically ventilated patients with PEEP ≥ 10 cmH2O (\"high level\") and without spontaneous breathing were prospectively included. Volume responsiveness was assessed by a positive PLR-test, defined as an increase in pulse-contour-derived cardiac index (CI) during PLR ≥ 10%. The PEEP-test consisted in reducing PEEP from the high level to 5 cmH2O for one minute. Pulse-contour-derived CI (PiCCO2) was monitored during PLR and the PEEP-test.
We enrolled 64 patients among whom 31 were volume responsive. The median increase in CI during PLR was 14% (11-16%). The median PEEP at baseline was 12 (10-15) cmH2O and the PEEP-test resulted in a median decrease in PEEP of 7 (5-10) cmH2O, without difference between volume responsive and unresponsive patients. Among volume responsive patients, the PEEP-test induced a significant increase in CI of 16% (12-20%) (from 2.4 ± 0.7 to 2.9 ± 0.9 L/min/m2, p < 0.0001) in comparison with volume unresponsive patients. In volume unresponsive patients, PLR and the PEEP-test increased CI by 2% (1-5%) and 6% (3-8%), respectively. Volume responsiveness was predicted by an increase in CI > 8.6% during the PEEP-test with a sensitivity of 96.8% (95% confidence interval (95%CI): 83.3-99.9%) and a specificity of 84.9% (95%CI 68.1-94.9%). The area under the receiver operating characteristic curve of the PEEP-test for detecting volume responsiveness was 0.94 (95%CI 0.85-0.98) (p < 0.0001 vs. 0.5). Spearman\'s correlation coefficient between the changes in CI induced by PLR and the PEEP-test was 0.76 (95%CI 0.63-0.85, p < 0.0001).
A CI increase > 8.6% during a PEEP-test, which consists in reducing PEEP to 5 cmH2O, reliably detects volume responsiveness in mechanically ventilated patients with a PEEP ≥ 10 cmH2O. Trial registration ClinicalTrial.gov (NCT 04,023,786). Registered July 18, 2019. Ethics Committee approval CPP Est III (N° 2018-A01599-46).

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Magnetic Resonance Thermometry Imaging (MRTI) holds great potential in laser ablation (LA) monitoring. It provides the real-time multidimensional visualization of the treatment effect inside the body, thus enabling accurate intraoperative prediction of the thermal damage induced. Despite its great potential., thermal maps obtained with MRTI may be affected by numerous artifacts. Among the sources of error producing artifacts in the images., the cavitation phenomena which could occur in the tissue during LA induces dipole-structured artifacts. In this work., an analysis of the cavitation artifacts occurring during LA in a gelatin phantom in terms of symmetry in space and symmetry of temperature values was performed. Results of 2 Wand 4 W laser power were compared finding higher symmetry for the 2 W case in terms of both dimensions of artifact-lobes and difference in temperature values extracted in specular pixels in the image. This preliminary investigation of artifact features may provide a step forward in the identification of the best strategy to correct and avoid artifact occurrence during thermal therapy monitoring. Clinical Relevance- This work presents an analysis of cavitation artifacts in MRTI from LA which must be corrected to avoid error in the prediction of thermal damage during LA monitoring.

Blood pressure (BP) is a key parameter in critical care and in cardiovascular disease management. BP is typically measured via cuff-based oscillometry. This method is highly inaccurate in hypo- and hypertensive patients. Improvements are difficult to achieve because oscillometry is not yet fully understood; many assumptions and uncertainties exist in models describing the process by which arterial pulsations become expressed within the cuff signal. As a result, it is also difficult to estimate other parameters via the cuff such as arterial stiffness, cardiac output and pulse wave velocity (PWV)-BP calibration. Many research modalities have been employed to study oscillometry (ultrasound, computer simulations, ex-vivo studies, measurement of PWV, mechanical analysis). However, uncertainties remain; additional investigation modalities are needed. In this study, we explore the extent to which MRI can help investigate oscillometric assumptions. Four healthy volunteers underwent a number of MRI scans of the upper arm during cuff inflation. It is found that MRI provides a novel perspective over oscillometry; the artery, surrounding tissue, veins and the cuff can be simultaneously observed along the entire length of the upper arm. Several existing assumptions are challenged: tissue compression is not isotropic, arterial transmural pressure is not uniform along the length of the cuff and propagation of arterial pulsations through tissue is likely impacted by patient-specific characteristics (vasculature position and tissue composition). Clinical Relevance- The cuff interaction with the vasculature is extremely complex; existing models are oversimplified. MRI is a valuable tool for further development of cuff-based physiological measurements.